Translation initiation is a key point in the regulation of gene expression. A central event in this process is the selection of the initiation codon in the mRNA. If the incorrect initiation codon is selected by the translational machinery, a miscoded protein will be produced, which could have disastrous consequences for the cell. My lab has developed a variety of in vitro tools for studying this key step in protein synthesis, and, together with Alan Hinnebusch's lab at the NIH/NICHD, we have recently made significant strides in understanding the molecular mechanics of start codon recognition. One valuable set of tools we lack, however, are small molecules that can modulate the fidelity of initiation codon recognition by the translational machinery. To address this need, we will conduct a screen for compounds that alter the fidelity of initiation codon recognition in vivo in yeast using a dual luciferase reporter system. The most promising of these compounds will be evaluated for efficacy, toxicity and general mode of action. In addition to their value as research tools, compounds discovered in this screen would be potentially important leads for drug development. Variants of many serious genetic diseases are caused by mutations involving initiation codons, and it is possible that these diseases could be ameliorated by drugs that alter the fidelity of start codon recognition, allowing sufficient protein to be produced from the mRNA with the aberrant start site. Compounds that alter the fidelity of start codon recognition might also prove useful for the development of novel anticancer or antifungal agents. This is a high-risk project and a new direction for my lab. However, if even one effective compound is discovered it would be a major breakthrough for the field of eukaryotic translation research and could provide an important starting point for future drug development. Proteins are the workhorses of our cells. They do the essential tasks that keep cells alive and allow them to grow, divide, and specialize into specific types, such as heart or kidney cells. Proteins are made by a cellular machine called the ribosome that reads information contained in our genes to make the corresponding proteins. A messenger molecule called messenger RNA (mRNA) carries a gene's instructions to the ribosome. For the instructions to make sense, the ribosome needs to start reading the mRNA at the correct starting point. When physiological changes in the cell or mutations cause a change in the starting point, diseases such as phenylketonuria, Tay-Sachs and diabetes insipidus can result. Currently there are no known drugs that can push the ribosome to start at the correct point on altered mRNAs, ameliorating these and other diseases. Using a vast collection of chemical compounds housed and maintained by the National Institutes of Health and Johns Hopkins University School of Medicine, we will search for molecules that alter how the ribosome selects the starting point in the mRNA. These compounds could ultimately be developed into drugs to treat diseases such as Tay-Sachs, as well as certain types of infections or cancer. These chemicals would also be valuable tools for scientists seeking to better understand how the ribosome works. A deeper understanding of this complex cellular machine could lead to new approaches to treat the myriad diseases that affect the ribosome's function. [unreadable] [unreadable] [unreadable]